POS1206 SARCOPENIA IS A MARKER OF MUSCLE DAMAGE ASSOCIATED WITH DISEASE SEVERITY AND DISABILITY IN PATIENTS WITH INFLAMMATORY MYOPATHIES
Authors: M. Giannini, A. L. Charles, L. Debrut, F. Goupilleau, J. Blaess, R. M. Javier, B. Geny, A. Meyer
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Inflammatory myopathies (IM) are autoimmune diseases characterized by muscle inflammation and weakness. Damage is a prognostic factor in IM, but its assessment in daily clinical practice represents an unmet need. In other settings than IM, a low muscle mass and strength (referred as sarcopenia) have been linked with disability, decreased quality of life and increased mortality. Sarcopenia has never been studied in IM. <h3>Objectives</h3> To determine the prevalence and clinical significance of low muscle mass, strength and sarcopenia in inactive or low-activity IM. <h3>Methods</h3> Adult IM patients according to 2017 ACR/EULAR classification criteria with disease duration ≥12 months, creatine kinase (CK) serum level &lt;500 U/l, &gt;6-month stable medication and Physician Global Activity ≤3/10 were prospectively enrolled. Healthy age and sex-matched volunteers were enrolled as controls. Activity and damage were assessed according to the IMACS scores. Appendicular lean mass (ALM) and strength were measured by dual-energy X-ray absorptiometry (DXA), hand-held dynamometer and manual muscle testing (MMT). Physical performance, disability, respiratory volumes and maximum inspiratory (Pimax) and expiratory pressures (Pemax) were assessed. Sarcopenia was diagnosed according to the EWGSOP consensus<sup>[1]</sup>. Several myokines were measured in the blood. <h3>Results</h3> Forty IM patients (27 females, 68%) with an average age of 59.9 years (±14) and 30 healthy age and sex-matched volunteers (19 females, 63%) were prospectively enrolled. Eight patients suffered from dermatomyositis (DM), twelve from immune-mediated necrotizing myopathy (IMNM), eleven from anti-synthetase syndrome (ASS), nine from scleromyositis (SM) since 4.6 years (2.9 - 8.4). At the enrolment, MMT-8 was 140/150 (135.3-147), MMT-12 was 213/220 (203.3-216.8), CK were 122 U/l (87.5-195.5). ALM correlated with MMT-8 (r=0.4, p=0.01), MMT-12 (r=0.5, p=0.004), grip strength (r=0.3, p=0.05), 6-minute walking distance (6mWD) (r=0.6, p=0.0002), time to drink a 20 centilitre cup (r=-0.5, p=0.001), vital capacity (r=0.5, p=0.02), Pimax (r=0.6, p=0.03) and Pemax (r=0.6, p=0.04), severity (r=-0.5, p=0.003), extension (r=-0.4, p=0.007) and global (r=-0.6, p=0.0001) damage. Grip strength correlated with MMT-8 (r=0.5, p=0.003), MMT-12 (r=0.4, p=0.005), ALM (r=0.3, p=0.05), 6mWD (r=0.4, p=0.02), global damage (r=-0.4, p=0.008), HAQ score (r=-0.3, p=0.04). Seven out of forty myositis patients (17.5%) were sarcopenic (vs 0% in the control group). They suffered from IMNM (57% vs 24%), DM (29% vs 18%) and SM (14% vs 24%). No patient suffered from ASS (0% vs 33%). Sarcopenic patients had history of severe muscle involvement: loss of walking ability (vs 21%, p=0.0002), higher maximum CK values (5998 U/l (3488-6500) vs 1636 (626-5000), p=0.07), respiratory muscles impairment (29% vs 3%, p=0.02) and myocarditis (43% vs 3%, p=0.001); and they more frequently required intravenous immunoglobulins (86% vs 33%, p=0.03), plasmapheresis (29% vs 3%, p=0.02) and/or unconventional immunosuppressants (57% vs 27% p=0.1). By contrast, extramuscular involvements were less frequent (43% vs 76%, p=0.08). None of sarcopenic patients had inflammatory joint involvement during the follow-up (0% vs 49%, p=0.02). At the time of evaluation, sarcopenic patients had lower MMT-8 (131/150 vs 142/150, p=0.004) and MMT-12: 199/220 vs 215/220, p=0.004), reduced 6mWD (196 (±80) vs 478 (±89) meters, p&lt;0.0001) and HAQ score (2.1 (1.2-2.8) vs 0.6 (0.3-1), p=0.0008). Irisin and secreted protein acidic and rich in cysteine serum levels were lower in sarcopenic compared to non-sarcopenic patients (respectively p=0.008, p=0.001). <h3>Conclusion</h3> Muscle mass measurement by DXA and muscle strength measurement by hand held dynamometer are simple and relevant tools to assess muscle damage in IM. Sarcopenia is frequent in patients with inactive or low-activity IM. It is associated with important skeletal damage, poor function and disability. <h3>Reference</h3> [1]Cruz-Jentoft AJ et al. Age Ageing. 2019 Jul 1;48(4):601. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Margherita Giannini: None declared, Anne-Laure Charles: None declared, Léa Debrut: None declared, Fabienne Goupilleau: None declared, Julien Blaess: None declared, Rose-Marie Javier: None declared, Bernard Geny: None declared, alain meyer Grant/research support from: CSL Behring.